This invention relates in general to body and frame assemblies for vehicles. More specifically, this invention relates to an improved structure for a splice joint for connecting a pair of open channel side rail sections in a vehicular body and frame assembly that focuses stresses imposed thereon away from the longitudinal edges of the structural members.
Many land vehicles in common use, such as automobiles, vans, and trucks, include a body and frame assembly that is supported upon a plurality of ground-engaging wheels by a resilient suspension system. The structures of known body and frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate body and frame assembly, the structural components of the body portion and the frame portion are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate body and frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modern vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized body and frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit that is resiliently supported upon the vehicle wheels by the suspension system. Unitized body and frame assemblies of this general type are found in many relatively small modern vehicles, such as automobiles and minivans.
One well known example of a separate type of vehicular body and frame assembly is commonly referred to as a ladder frame assembly. A ladder frame assembly includes a pair of longitudinally extending side rails that are joined together by a plurality of transversely extending cross members. The cross members connect the two side rails together and provide desirable lateral, vertical, and torsional stiffness to the ladder frame assembly. The cross members can also be used to provide support for various components of the vehicle. Depending upon the overall length of the vehicle and other factors, the side rails of a conventional ladder frame assembly may be formed either from a single, relatively long structural member or from a plurality of individual, relatively short structural sections that are secured together. For example, in vehicles having a relatively short overall length, it is known to form each of the side rails from a single integral structural member that extends the entire length of the vehicle body and frame assembly. In vehicles having a relatively long overall length, it is known to form each of the side rails from two or more individual structural sections that are secured together, such as by welding, to provide a unitary structural member that extends the entire length of the vehicle body and frame assembly.
Traditionally, the side rails of known vehicle body and frame assemblies have been formed from open channel structural members, i.e., structural members that have a non-continuous cross sectional shape (U-shaped or C-shaped channel members, for example). Thus, it is known to use a single integral open channel structural member to form a side rail that extends the entire length of the vehicle body and frame assembly, as described above. Additionally, it is known to secure a plurality of such open channel structural members together to form the individual sections of a unitary side rail for a vehicle body and frame assembly, as also described above. It will be appreciated that each of such open channel structural members has a pair of longitudinally extending edges. It is known that these longitudinal edges are somewhat weaker than the interior portions of the structural members. Thus, when excessive stresses are imposed upon a side rail during use, cracks usually initiate at the longitudinally extending edges of the structural members and migrate inwardly toward the interior regions thereof.
A number of joint structures are known for permanently joining two open channel structural members to provide a unitary side rail in a ladder frame assembly. One known joint structure is commonly referred to as a butt joint. In a typical butt joint, a rearward end of a first side rail section is disposed directly adjacent to a forward end of a second side rail section, with no overlapping of the two side rail sections. The two adjacent ends of the side rail sections are then permanently secured together, such as by welding, to provide a unitary side rail. Another known joint structure is commonly referred to as a splice or overlap joint. In a typical splice joint, a rearward end of a first side rail section partially overlaps a forward end of a second side rail section. The two overlapped ends of the side rail sections are then permanently secured together, such as by welding, to provide a unitary side rail.
Although known butt and splice joint structures have been effective, it has been found that the such joint structures tend to focus stresses imposed upon the side rail at or near the longitudinal edges of the open channel structural members. Thus, it has been necessary to design known joint structures to accommodate the maximum loads at the longitudinal edges of the structural members. As a result, the other portions of the structural members are, in essence, over-designed for the loads intended to be carried thereon. This can result in the use of thicker or heavier materials to form the structural members, adding undesirable additional weight to the vehicle body and frame assembly. Thus, it would be desirable to provide an improved structure for a splice joint for connecting a pair of open channel side rail sections in a vehicular body and frame assembly that focuses stresses imposed thereon away from the longitudinal edges of the structural members.